where did the 70s take the horses

EDIT KK beat me to it

Actually, Rani, "it's both."

Smog controls for certain took their toll. Reduced performance advance curves, leaned out carburetors, and in general, lower compression and diddled cam timing

And you are right "they" changed from gross HP to "net" HP

"Net" is SUPPOSED to be a more relevent representation, taking into account "the actual stuff" that an engine has to have to operate, including alternator, PS pump, water pump etc

BUT THE thing is, "numbers" get "diddled."

My favorite example (and there are many) is ratings on air compressors

"Once upon a time," compressors were rated by the air in cfm that they would output at 90PSI operating pressure

Then in the ?60's? Wards or Sears or someone "discovered" 'HEY' if we rate OURS at 40 psi instead of 90, THE NUMBERS GO UP.

THEN somebody discovered that if you rate them by scfm (suction, or intake, or atmosperic pressure) the numbers REALLY go up

So the very same compressor, at these three different ratings, "seems" bigger at 40 psi, and bigger yet at SCFM than it does at 90 PSI

The point is that "numbers" are only as good, meaningful, and accurate as the guy's ethics who wrote them

Battery ratings, many other things, are a Great Big Lie.